Tires are a combination of many different parts, some of which are rubber and some of which are fabric and/or steel. These parts come together at a tire assembly machine (“TAM”). The TAM is a large horizontal drum where a tire builder who operates the TAM will first slip bead subassemblies over the drum. Thereafter, an inner liner layer is created by wrapping multi-layers of elastomeric rubber onto the drum. The ends of the layers are spliced together to make what is a tube. A tire casing is built with the application of one or more body plies. At this point, the components of the tire more resemble a wheel than a tire and the casing has to be put into the shape and size of a tire. This is done with a rubber tire former bladder. This bladder acts like an inner tube and inflates inside the layers which form the tire casing. At the same time, the TAM drum, which is like a mandrel and over which the layers have been wrapped, shortens itself and pushes the outside edges of the various layers together.
The edges of the body plies of the casing also have to be folded over the tire beads to secure the beads to the casing. This folding is done by turn up bladders (TUBs), which turn the body plies over the bead(s) to secure the plies and casing to the beads. Thereafter, belts and treads are applied, the TAM spun and the various parts are pressed together to make a green tire which then is cured.
Tire former bladders are highly elastic and may be used to shape the uncured tire to place and stabilize plies and tread. These former bladders are subjected to multiple inflations and deflations and have fairly large areas which must readily release from the inner liner of the tire so that the former bladder may be used with another tire forming in another cycle of tire making. In this respect, tire former bladders are unique and different from turn up bladders. The inflations and deflations of tire former bladders cause abrasion on the internal surface of the bladder as it deflates and the internal surface of the bladder folds onto itself. In the past, this rubbing has caused abrading the internal surface of the bladder. Hence the tire former bladder not only must be strong, but ideally should be abrasion resistant to withstand thousands of duty cycles under dynamic high strain conditions, yet the tire former bladder also must readily release from large areas of the uncured tire when deflated. In contrast, turn up bladders do not experience strain and wear from having large areas having to release from green tires. Tire former bladders in the past have readily stuck to green tires disrupting production and the cycle life of the tire former bladder.
U.S. Pat. No. 5,188,904 to Graves describes TAMs and the use of bladders, most specifically mentioning turn up bladders (TUBs), which have a release agent on the outer surface of that elastomeric bladder. Graves has considerable detail as to the use and composition of the release agent on the exterior surface of the TUB. Graves also mentions that the TUBs have an optional fabric reinforcement, but does not discuss the problem of abrasion of the inner surface of tire former bladders, how much stretch the fabric has or should have and where the fabric reinforcements are made a part of the TUB. Indeed tire former bladders need to be capable of more stretch than typical TUBs because tire former bladders do stretch more, and silicone release agents do not adhere well to the outer surface of the former bladder.
Fabric reinforcing agents also are known in tire former bladders. These fabric reinforcing agents, however, were on the inside and/or outside surface of elastomer bladder and did not address an abrasion problem together with a problem concerning the release of the outer surface of the former bladder from the green tire as the bladder as the bladder went through multiple work cycles in forming tires. Known fabric reinforcing agents on the inside surface of the former bladder did not address the ability of the reinforcing agent or fabric to adhere to the bladder, yet reduce friction at the inner surface of the bladder as it is inflated and deflated. Bladders with reinforcing agents on their outside surface did not address or solve the releasability of the bladder's outside surface from the inner liner of the tire being formed.